Electrodes containing supported platinum catalyst particles are used in electrochemical cells, such as fuel cells. For example, in a conventional hydrogen fuel cell, a supported platinum catalyst is used to oxidize hydrogen gas into protons and electrons at the anode of the fuel cell. At the cathode of the fuel cell, another supported platinum catalyst triggers an oxygen reduction reaction (ORR), leading to the formation of water.
The platinum catalyst particles can be core-shell catalyst particles having a palladium core and a platinum shell. Core-shell catalyst particles have an increased ORR activity compared to previous platinum catalysts, such as platinum nanoparticles. Core-shell catalyst particles also have a reduced material cost because expensive platinum is only used to cover the outer surface of the core.
The platinum shell is an atomically thin layer of platinum atoms that encapsulates the palladium core. While the platinum atoms cover the majority of the core, the shell can have voids, holes or gaps, known as pinholes. These pinholes expose the palladium core.